The South Americans broke five times and overcame three break points to extend the series. The visitors need to sweep today’s reverse singles to become the first team in 72 years to rally from a 2-0 deficit.

“We played a great game. We’re in very good shape, and the series is still alive,” Nalbandian said. “Our hope is intact.”

The 11th-ranked Del Potro needs to recover quickly from his exhausting, nearly five-hour loss to David Ferrer on Friday.

“It’s normal (Del Potro) feels tired but I think he’s ready for the challenge tomorrow,” Argentina captain Tito Vazquez said. “To take it to a fifth match we have to win the fourth and that means we have to beat Rafa Nadal. It’s not so simple.”

Nadal and Ferrer practiced on Saturday. The pair are a combined 27-0 on clay for Spain, which hasn’t lost a home series on clay since 1999.

“I’m not pessimistic. Tomorrow we have Nadal and Ferrer to win one point,” said Spain captain Albert Costa, who expected Nalbandian to replace Juan Monaco should the final stretch to a fifth match.

Lopez and Verdasco again failed to follow up an impressive sweep of the opening singles by Nadal and David Ferrer. They also lost in the semifinals against France in which they won only three games. Their cup win-loss record together stands at 7-6.

“Today was one of those days I’d like to forget,” Lopez said. “It was my worst ever Davis Cup match.”

The Argentine section of fans was boisterous throughout, with Nalbandian volleying home the winner to break Lopez’s serve in the fifth game as the visitors served out the set.

Nalbandian played for the first time since October because of various injuries. He and Schwank took a 4-0 lead in the second to take command of the match.

In the third set, after the Spanish pair managed to get the crowd of more than 20,000 fired up with a break chance in the sixth game, Argentina saved two break opportunities before Schwank ended the suspense with a volley at the net to hold serve.

Schwank served out the victory in just under two hours when Verdasco volleyed into the net to help Nalbandian to his 12th doubles victory in the competition, equaling Guillermo Villas’ record. Nalbandian improved his overall cup record to 34-10 in his third final appearance.

Argentina has never won in three previous final appearances, including 2008 when it lost to Spain in Mar del Plata.